The broad aim of this research is to develop an occupational exposure monitoring and control strategy, based on time-activity data for specific tasks, to constrain exposures to acceptable levels and minimize reliance on invasive biological measurements. Recently an intervention program developed to eliminate high blood lead levels in Connecticut bridge construction workers was shown to be effective. (Vork et. al., submitted) (Appendix A). This intervention program used contract specifications to require the lead health protection program and paid the expenses incurred by contractors to ensure that it would be successfully implemented. Among many strategies, frequent blood lead monitoring was required. These tests were used to alert employers and sometimes require them to reduce future exposures to airborne lead in specific workers. In addition to blood lead monitoring, the lead health protection program also required comprehensive industrial hygiene monitoring. The data collected during both the blood lead and the industrial hygiene monitoring programs provide the detailed information required for this research goal to be pursued in the context of lead exposure in bridge rehabilitation work. This research proposes to: use the blood lead data and time- activity patterns from the cohort involved in the Connecticut intervention program to estimate recent lead exposure (i.e. the cumulative lead intake from work over the past 30 day period); to use the Categorization and Regression Tree (CART) analysis of one half of the Connecticut cohort to determine the predictive value of various task, personal and environmental variables on cumulative lead intake as estimated in specific aim one; to validate the regression model derived in Specific Aim 2 using the other half of the data from the Connecticut intervention program cohort; and explore the implications of the regression model for identifying: a) cost-effective surveillance requirements for ongoing exposure control programs including the potential deficiencies in the Connecticut data set: and b) efficacious control strategies